The present invention relates to a medical catheter and more particularly to a catheter for the transvascular deployment of expandable medical devices, such as an intravascular embolic filter device, in a collapsed condition.
The device as described herein relates to a carotid angioplasty procedure with an intravascular filter being placed distally to capture procedural emboli being released. Other medical procedures warrant the use of distal protection systems. Angioplasty and stenting of surgically implanted Saphenous Vein grafts that have stenosed and primary treatment of Renal artery stenoses are applicable also. Indeed, the insertion of embolic protection devices to protect patients during any vascular surgery is envisioned as being applicable to this invention.
A particularly useful form of embolic protection device in the form of a filter element for placing in a desired position has been described in our co-pending patent application No. WO 99/23946 the contents of which are incorporated herein by reference. For example, this filter element is compressed into a housing or pod to advance it to the required location in a vessel. Once in situ the housing is withdrawn or the filter element is advanced. This allows the compressed filter element to expand to the required size and occlude the vessel except for the path or paths provided through the filter which thus provides a pathway for blood and has means for capturing and retaining undesired embolic material released during the surgical operation or percutaneous interventional procedure.
There are difficulties with such expandable devices, whether they be filters or other devices in that firstly they have to be correctly and efficiently compressed and retained within the pod so that when released from the pod, they will expand to assume the correct shape and will not have been distorted by the compression within the pod. The problems of distortion or incorrect expansion tend to be exacerbated if the medical device is stored for long periods within the pod prior to use. Secondly, it is important that the pod and the catheter tube itself be manipulated to the site of use without causing damage to, for example, the arteries through which it is being manipulated. Difficulties may arise if, for example, the catheter tube, or more particularly the pod as the pod effectively leads in the insertion, were to damage the artery sidewall and thus cause for example a break-away of atherosclerotic plaque from the carotid arteries.
Essentially this leads to certain requirements. The device needs to be efficiently compressed. The resulting compressed device needs to be manipulated in its pod as efficiently as possible. Further, there is a need for loading such catheters in a way that will facilitate their use on unloading.
It is known to mount implantable medical devices at a distal end of a delivery catheter for transvascular deployment. Upon reaching a desired location within a patients vasculature the catheter is withdrawn relative to the medical device thus allowing the medical device to expand or be expanded within the blood vessel. In the prior art WO98/07387 and U.S. Pat. No. 5,064,435 show stent delivery systems essentially comprising a catheter with a stent mounted in a collapsed state at a distal end of the catheter under a retractable outer sheath. An abutment within the bore of the catheter spaced proximally from the distal end of the catheter prevents retraction of the stent as the outer sheath is withdrawn over the stent. Each of these devices has at least two main components, namely an inner catheter and an outer sheath which is slidably retractable on the catheter to expose the stent for deployment.
These deployment catheters need to have lateral flexibility in order to manoeuvre through the vascalature but at the same time be sufficiently pushable so that they can be steered and manipulated through the vascalature. The mounting of a medical device within the distal end of the catheter either greatly limits the size of the medical device that can be accommodated or necessitates enlargement of the catheter which restricts access of the catheter within the vascalature of a patient.
Catheters of this type tend to be relatively long and the loading of a medical device within the distal end of the catheter prior to use can be a somewhat cumbersome operation for the surgeon. The length of the catheters makes them unwieldy and difficult to keep sterile. There is also a difficulty in ensuring air is excluded from the medical device and catheter during loading.
The present invention is directed towards overcoming these problems.
According to the invention there is provided a catheter for the transvascular deployment of a medical device, the catheter comprising an elongate tubular body having a proximal end and a distal end, a tubular housing being formed at the distal end of the body for reception of the medical device, a deployment means for engagement with the medical device, being movable through the housing to move the medical device between a stored position within the housing and an in-use position externally of the housing, characterised in that the housing comprises a tubular thin-walled medical device embracing pod fixed at the distal end of the body, the pod extending outwardly from the distal end of the body and forming an extension thereof. Conveniently, the pod and the catheter body form a single integral unit for deployment of the medical device.
Preferably the catheter body has an inner tubular core encased within a concentric thin-walled tubular outer sheath which is fixed to the core, the sheath being extended outwardly of a distal end of the core to form the pod.
The advantage of using the thin-walled tube is that the maximum volume to retain the medical device for deployment is achieved. Further the pod is relatively flexible on the catheter further facilitating its manipulation and passage through vasculature to the desired site of use.
Preferably the inner tubular core is formed from a steel spring, but may alternatively be formed from polymeric material. Any suitable material may be used as the core is now covered by the thin-walled tubular outer sheath which is effectively the important tube, being the vessel contact surface. Alternatively, a thin walled pod may be achieved by locally thinning a polymeric tube at the distal end of the tube.
Preferably the thin-walled tube is manufactured from a low friction material and ideally is manufactured from polytetrafluoroethylene (PTFE) often sold under the Registered Trade Mark TEFLON. The thin walled tube may alternatively be manufactured from any other suitable thin walled material of low friction coefficient or employing a friction reducing agent or component to minimise the friction coefficient. The advantage of this is that firstly the catheter will not damage arteries, for example the carotid, knocking off atherosclerotic plaque. Further this will allow the easy removal of the implant from the catheter.
Where the outer thin walled tube is formed of PTFE, it would typically have a thickness of less than 0.004 inches (0.1 mm). The thickness of thin walled tubes of other materials may vary somewhat depending on the characteristics of the material being used.
In another aspect the invention provides a method of loading such a catheter comprising:
inserting a loading tube into the pod at a free end of the outer thin-walled tube; and
compressing the medical device and delivering the compressed medical device through the loading tube into the pod.
The problem is that if one did not insert the loading tube into the pod the thin-walled tube would collapse in compression when trying to insert the medical device. The use of the loading tube prevents such collapse.
Preferably the loading tube is a further thin-walled tube which is inserted into the pod for smooth delivery of the medical device into the pod.
Ideally the medical device is compressed by delivering the filter device through a funnel and into the loading tube which is mounted at an outlet of the funnel.
In another aspect the invention provides a delivery system for transvascular deployment of a medical device, the system comprising a catheter in combination with an associated separate loading device which is operable to collapse the medical device from an expanded in-use position to a collapsed position for reception within the pod.
Preferably the loading device comprises means for radially compressing the medical device.
In a particularly preferred embodiment the loading device comprises a funnel having an enlarged inlet end and a narrowed outlet end, the outlet end being engageable within the pod.
In another embodiment, the loading device comprises a main support having a funnel-shaped bore formed from a frustoconical filter device receiving portion terminating in a cylindrical portion formed by a thin-walled loading tube projecting from the main support. This funnel-like arrangement is a very suitable arrangement of loading a pod on the catheter with a compressible filter device.
Ideally the cone angle is between 15xc2x0 and 65xc2x0 and preferably may be between 35xc2x0 and 45xc2x0. This allows a sufficiently gentle compression of a filter device, particularly one of a polymeric material.
In one particularly preferred embodiment of the invention, the main support is formed from the material available under the trade mark xe2x80x9cPerspexxe2x80x9d and the thin-walled loading tube is formed from PTFE material. The Perspex gives a smooth surface.
Preferably the loading tube is mounted on the main support on a metal spigot at an outlet end of the funnel.
In a still further aspect the invention provides a pack for an elongate intravascular catheter of the type comprising a tubular body with a proximal end and a distal end, the distal end adapted for reception of a medical device, the pack comprising a tray having means for releasably holding the distal end of the catheter relative to an associated catheter loading device in a cooperative juxtaposition on the tray, the loading device being operable to collapse the medical device from an expanded in-use position to a collapsed position for reception within the pod. This facilitate raid and correct loading of a medical device within the catheter.
Preferably the tray has a liquid retaining bath formed by recess in the tray, the bath having a depth sufficient to accommodate in a totally submerged state the distal end of the catheter and a medical device for submerged loading of the medical device into the catheter.
In another embodiment the tray has a catheter holding channel communicating with the bath, the channel defining a pathway around the tray which supports the catheter in a loading position on the tray.
Preferably the means for securing the catheter within the channel comprises a number of retainers spaced-apart along the channel, each retainer comprising two or more associated projections which project inwardly from opposite side walls of the channel adjacent a mouth of the channel, the projections being resiliently deformable for snap engagement of the catheter within the channel behind the projections.
Conveniently a ramp is provided at an end of the channel communicating with the bath to direct a distal end of the catheter towards a bottom of the bath.
In another embodiment means is provided within the bath for supporting the distal end of the catheter above the bottom of the bath. Preferably said supporting means is a step adjacent the channel.
In another embodiment means is provided within the bath for supporting a catheter loading device for engagement with the distal end of the catheter to guide a medical device into the distal end of the catheter. Preferably said means comprises a recess in a side wall of the bath for reception of a funnel with an outlet pipe of the funnel directed towards the channel for engagement within the distal end of the catheter.
Ideally, it will be appreciated that the device for loading the catheter with a compressible filter device such as described above may be used in conjunction with this pack. The advantage of this is that the filter device can be submerged in a saline bath during loading into the pod which ensures that air is excluded from the filter device when loading as it would obviously cause medical complications if air was introduced to the bloodstream during an angioplasty and stenting procedure. The tray system with the catheter distal end submerged, combined with appropriately designed catheter proximal end and standard device flushing techniques can ensure a fluid filled device is introduced to the vasculature.